Air duct systems, particularly in domestic residences, often provide air registers at floor level. Usually floor registers are installed where ducts run between floor joists in a multi-story building. The register may either be a supply or a return, although supply registers are more common. Where the register is in the floor, and if there is any liquid spilled on to the floor, it can flow through the register into the air duct system. Some liquid may flow around the register and simply collect on the ceiling of the room below. This problem occurs in an acute form where for example a bathroom or a laundry room is installed with floor registers. In such rooms, where the likelihood of liquids being spilled is more common, any liquid which flows down through a floor register opening will usually escape from the duct work and may damage the ceiling of the room beneath. Simply repairing the ceiling is not a solution. The problem may occur repeatedly.
Clearly it is desirable to provide a liquid drain, which can be secured beneath the floor, around the opening for the floor register. It is however apparent that any such liquid drain must also accommodate air handling facilities, to permit air to pass through the register either from, or back into the HVAC duct system.